Grinding machine



O. E. HILL GRINDING MACHINE Dec. 1, 1953 3 Sheets-Sheet'l Filed Dec. 11, 1951 o. E. HILL GRINDING MACHINE Dec. l, 1953 5 Sheets-Sheet 2 Filed Dec. 11, 1951 Dec. l, 1953 o. E. HILL` 2,660,837

GRINDING MACHINE Filed Dec. ll, 1951 3 Sheets-Sheet 3 RELA YE ANB MUTUR 5 VV/ TCH 5 www /70 n l-TM/erff'orr /VA E. H/LL Amma), i

Patented Dec. 1, 1953 UNITED.- STATES- PATENT OFFICE Oiva' E.1Hill, West Boylston; Mass., assignorto Norton Company, WorcestenMass., a corporation of Massachusetts ApplicatibnDecember 11, 1951, Serial Noi 261,030

17 Claims. (C1. 51-95) This invention relates tol grinding machines,` and more particularly to a1grinding'machine for correlating surface speed of the work" being ground and the cutting rate of the grinding wheel.

One of the objects off-this invention is to provide a simple and'A practical grinding machine for dependably controlling and correlatingwork surface speed and cutting rate of the grinding wheel. Another object is rto provide a grinding apparatus in which relative'feeding movement of work surface to the grinding'wheelmay be controllably interrelated in a thoroughly practical and dependable manner; another object is to carry out the just stated. objects by mechanisms and controls that will provide a suitable range of flexibility to meet'not-only the requirements vfor grinding a givenwork-piece, but also the varying requirements of otherztypes' orV kinds of Workpieces to be ground. Another object is Yto provide a grinding apparatus rof practical and inexpensive construction for controllably varying the surface speed of the work-piece during grindingoperation thereon by the grinding Wheel, and well adapted to meet the varying. conditions of hard practical use. Another" object is to provide Va grinding apparatus in which relative feed movement between grinding wheel and work-piece may be dependablysynchronized with change in surface speed of the work-piece. Another object is to provide acompact and efficient variablespeed drive for the work-piece and controls therefor that will be .well adapted forcontrollable coaction with other elements of the grinding apparatus such, for example, as control of depth of cut of the grinding wheel.

Another object is -to provide simple, practical, and efficient hydraulic controls Afor variably correlating surface speed of the work and depth of cut of the grinding wheel. Another object is to provide an apparatus of the just-mentioned character for performing a grinding operation commencing with high'rate of stock-"removal and terminating in low 4rate of stock removalf which may be efficiently carried out.A

Another object is vingeneralto-provide an improved grinding apparatuszfof the' above-men` Other.v obj ectsvwill: be in "part" tioned character." obvious or Vin part/pointed A.out hereinafter.

The invention accordinglyfconsists: in the f feadicated in 4the following claimsi- Inithe accompanyingdrawings in which similar reference' characters refer;mv to: similar' parts throughout the several views-1- Figure l is fa front `elevatiorr= oiv fthe-completeY grinding i machine; certain'V parts of fthe dr1ve`- shafts. and pulleys .Joeing fshownlin brokenf= lines 2 with therbelting and bearing supports therefor purposely omitted to avoid confusion;

Figure 2 is av detached fragmentary end elevation showing certain features of drive, as seen Figure 3 is a detached end elevation on a larger scale of the head stockunit, substantially as seen along the line 3-3 of Figure l, certain parts being broken away;

Figure 4 isa detached enlarged vertical sectional view of a variable-'pitch drive pulley substantially as seen along :the line 4--4 of Figure 2;

Figure 5 is a fragmentary detached vertical sectional view through the grinding wheel slide and the wheel feedingmechanism to illustrate a possible form of mechanism for wheel feed;

Figure 6 shows in section several vof the various hydraulic mechanisms and shows diagrammatically the piping and'valveconnections and controls therefor.l

My invention is best illustrated in connection with so-called external cylindrical grinding, oftentimes referred to as center grinding, particularly where thework-piecerto be ground is supported and rotated by and on centers; accordingly, for purposes of illustration, in Figure l I have shown a grinding apparatus provided with a head stock unit I@ and a tail stock unit I I having centers l2 and It, respectively, for supporting the work-piece as by an arbor I4, so as to present, upon rotation, successive portions of the surface of the work-piece W to a grinding wheel I5 to grind it to cylindrical form. Head stockv I 0 and tail stock II are supported on a box-like frame or base I6 through the intermediary of a longitudinally slidable or reciprocable table II supported and guided by a longitudinally extending V-way I8 (Figure 3) and av companion fiatway 20, and an intermediate table 2| (Figures l and 3)` which rests flatwise on table I'I and relative to which it may be swivelled about a vertical axis, an axis usually provided by a suitable pivotal connection between the two tables in the form, for example, of aheavy cylindrical block 'or stud indicated at 22` in Figure l, there being clamping devices 23 at the respective ends of the two tables'to xthe swivel table 2I in the desired relation to thefslidingitable I 7. Head stock I0 and tail stock II rest 4directlyupon the swivel table'Z by which theyr are aligned and along which theyareadjustably positionable in' any.

suitable manner;

For example and as is better shown in Figure 3, the upper face of -swivel table-2l may slant downwardly and rearwardly', providing along its upper front edge a- V-shaped guide-part' 24 withfwh'i'ch the front-underside of the-'head stock and tail stock intert, .clamping dogs v2li at' the rear' of the-stocks,`A controlled bygbolts-Z and the `vnuts oflwhich are operable frorn'tlier front of the mato the horizontal axis of the grinding wheel I which is parallel to the path of longitudinal movement of the table I1 on the bed I6, so that the surface of a rotating work-piece may be ground to tapered form. The grinding wheel axis is provided by a spindle 21 (Figure 1) carried in suitable bearings in a grinding wheel slide 28 which is slidably mounted in usual manner on a pair of rearwardly and hence transversely extending ilat and V-ways 29 (Figures 1 and 5) provided in a rearward extension of the machine base I6 so that the grinding wheel is movable toward and away from the longitudinal table I1 or toward and away from the observer viewing Figure 1, the axis of wheel spindle 21 being parallel to the line of longitudinal traverse of table I1. Grinding wheel I5 is mounted on one end of spindle 21 which is driven by an electric motor 30 through driving connections at its other end, such as pulleys and V-belts (not shown) enclosed in a belt guard or casing 3 I Wheel slide 28 may be fed toward or away from the axis of the work support and along its ways 29 by a feed screw 33 (Figure 5) having shaft extensions 34 and 35 rotatably carried in suitable bearings (not shown); wheel slide 28 has a depending half-nut 31 which meshes with feed screw 33 and accordingly wheel slide and grinding wheel partake of movement toward or away from the work axis if the feed screw 33 is bodily moved (hydraulically, for example) or if it is given a rotary movement by any suitable means; for example, apparatus and mechanism for both bodily moving the feed screw and rotating it, with accompanying controls, may be employed, such as are disclosed in Silven Patent No. 2,522,485. However, to simplify an understanding of my invention, for purposes of illustration I have selected to show herein a simple form of manual drive of the feed screw 33 and illustrative and preferred form of power drive therefor and control interrelated, as is later described, with the drive of the work-piece W through the head stock I0.

Thus, there is mounted at the front of the machine base I6 (Figure l) a manually operable feed wheel 38 provided with suitable driving connections with the feed screw 33, such as a small gear 4I! (Figure 5) coaxial with the wheel 38 and meshing with a large gear 4I on the front end of feed screw shaft 34, whereby transverse movement of the wheel slide and grinding wheel I5 may be manually effected. Power drive of feed screw 33 I preferably effect hydraulically, as by a hydraulic motor generally indicated in Figures 1, 5, and 6 by the reference character 43; it may comprise a cylinder 44 provided with suitable brackets 45 (Figure 6) by which it is secured at the front of the machine base I6 in a position substantially as indicated in Figure 1, with its axis horizontal and extending lengthwise of the apparatus, As better shown in Figure 6, cylinder 44 is double-acting, having a reciprocable double-ended piston 46 therein provided with piston rings 41 and 48 at its respective ends, the intervening portion of the piston 46 having a rack 56 formed thereon which is exposed to an opening 5I in the cylinder wall to mesh with a pinion 52 on a transversesha'ft 53 that is supported in a suitable bearing in upward exten-V 4 sions of the cylinder 44 and that carries a gear 55 (Figure 5) that meshes with larger gear 4I on the feed screw shaft 34 (Figures 5 and 1). Depending on the direction of the stroke given the piston Y 46, feed screw 33 is rotated slowly in one direction or the other to feed the wheel slide and grinding wheel toward the axis of the work or to retract it from the work. In-feed movement of the grinding wheel is to take place during grinding action of the grinding wheel on the workpiece as, for example, where the width of the grinding wheel I5 is equal to or greater than the width of the work W to be ground, as is illustrated in Figure l. Relative axial setting between grinding wheel and work-piece W may be effected by setting the position of table I1'-2I lengthwise of the ways IIB-20 of the machine base I6, by any suitable means; longitudinal movement, including reciprocation, of table I1 2I may be manually effected, as by a hand wheel 51 (Figure 1) mounted at the front of the base I6 which, through suitable gearing enclosed in the gear cover or case 58, may drive a pinion 60 that meshes with a rack 6I (Figures 1 and 3) that extends lengthwise along the underside of table I1, or movement of the table may be effected in suitable strokes or steps or stages by a power drive, such as the hydraulic drive and controls disclosed in the Silven Patent No. 2,522,485, and such movement correlated to other mechanisms of the apparatus, particularly the traverse and feed movements of the grinding wheel slide 28, also as disclosed in the said Silven patent, depending upon the character of work-piece to be operated upon.

The tail stock I I (Figure 1) may be of any suitable construction and may have any suitable mechanism, illustratively a Vhand lever 63 (Figure 1), for controlling the center I3 to permit ready replacement and mounting of the worksupporting arbor I4 which is provided with a dog arm 64, preferably double-ended and extending to each side of the arbor I4 to engage with diametrically opposed dogs 65, 65 (Figures 1 and 3) which are carried by a driven face plate or head 66 (Figure 3) that is coaxial with the center I2; head 66 is provided with diametrically opposed radial slots 61, 61 through which the dogs 65, 65 project and along which they are adjustably positioned and fixed by clamping nuts 68, 68. As the head 66, with its driving dogs 65, 65, rotates at a suitable speed, the round work-piece W is correspondingly rotated for action thereon by the grinding wheel I5, and provision is made to controllably change or vary the speed of drive of the head 66 and hence the rate at which the surface of the work-piece W is progressively presented to the face of grinding wheel I5, preferably in correlation with change in rate of in-feed of the grinding wheel itself.

^ As a source of driving power I prefer to employ an electric motor, indicated at 10 in Figures 1` and 3; the head stock I0 is constructed substantially in the form of a casing-like housing having a kmore or less at, rearwardly inclined top wall, indicated at 1I in Figure 3, and projecting upwardly from its front wall; it has a long boss 12 (Figures 1 and 3) that has a longitudinal bore to receive a long hinge pin 13 the ends of which extend into bored-out spaced bosses 14 and 15 that projectdownwardly'from a heavy plate 16 which carries the motor 10, being secured thereto, as by cap screws 11, the pivoting axis provided by pin 13 and the axis of motor shaft 18 being parallel tov each other and parallel to the. axis. ofv rotatable face plate or headf||. The resultant hinged Vmountingoffthe motor 'IU relative tof the housing ofy headA stock;Y

llllpermits'bodily-'displacement ofA the motor andits shaft 'frelativeto the"y headstocky housing, throughout a suitableV range and: for`A apurpose later described,v arrange on the order-r ofthat indicatedinuFigu're 3: by' the full-line and: broken-Y line Vvpositionsl of the motor-supporting plate, 16. Suitable means may-be provided' to adjustably limit the range ofswing ofthemotor support, such` as, for example, aA stop screw 80 (Figures 3`1'and; 1') carried-inV a bracket extensionV atthe fron-t; of'y thehead stock housing-'and ay screw-8| carried in a bracket at the rear-of4 the housing, theY motorlsupport 1|`-being controllablyshiftable inamanner later described:

Motor shaft 'IS/projects to the left'as seen in Figure lfthrough an arcuate slot 82- (Figures'Z and 3) formed inthe wall 83 of a belt-andpulley.- encasingguard lil;l provided with a removable cover'85; which is secured in any suitabie'way to the left end' wallof the head stock housing, andion the end ofshaft 18 issecured avariablemitch pulley Bit-(Figures l1',-2, andfl) to tairev aso-called V-belt 81-whch also runsover and drives a Vg rooved'pulley88 (Figures l and 2j)` whichhas coaxiallysecured to it, or coaxially constructedjtherewith to form a single unit, a stepped or cone pulley 90' (Figure 1)l which provides a jsuitable number of V-grooved pulleys of diiferent pitch diameters. The pulley unit Blij-991s located in the lower forward part of the vguardcasing 84 and is rotatably supported on a'. stud'` shaft 9| projectingA from the left wall of the `hpadstock casing andrigidly secured in the latterpby. means of a cylindrical block 92 integrally formed with the stud shaft 9|, but With the axis ofthe latter eccentric tothe axis of the block 92' (see also Figure) Extending lengthwise of the head stock casing I0, andV inL an upper portion thereof, and rotatably supported in suitable bearings (not shown) Acarried in the left and right end walls of the, casing, is a shaft 93` (Figure'l), whose left endg; projects into the guard' casingv 84 where it carriesja stepped or cone pulley 94providing a suitable number of differently diametered` V- shapedgrooyes that are complementary to those opi-'the stepped pulley 90; by means ofja V-belt 95,(Figures 2 and 3) pulley94 and its shaft 93 are driven from pulley 90 on stud shaftA 9| at a speedthat is selectible according to which com'- plementary pair of V-shapedv grooves is selected for the belt. Any suitable number ofr speed changes may thus be provided, and to simplify thedrawings and for purposes ofillustration, two steps are shown in each of the pulleys 90 and 94; thus providing for two such speed changes. The'block 92 which eccentrically carries the stud shaft 9|Y is seated in an appropriate cylindrical recess in the left wall of-head stock casing I9 so that it is rotatably adjustable in order thereby toadjust'the distance between shaft 9| and'shaft 93;; whenfnecessary to 'take Vup' stretch in the belt 95: Atthe-same time, for the full-line or normal at-restlposition of the tiltablemotor v'Hl andv its hinged support 'i6 `asshown in Figure, such adjusting shift of stud shaft 9| effects achange inthe distance between itself and the motor shaft A13, and-whilevariable-pitchpulley 86 (Figures-'l and 3) isself'-accommodating to such a shift, it ispreferred to compensatev therefor by adjusting thescrew 8|vr (Figure-3) to raise or lowersit andi-thus x the normal atz-rest-position ofmotor-ishaft 18 and itsdis'tancerfromthefshaft 9| so ;thatl.variableepitclrr'pulleyfl fisrsel'fendjusteing tolonez'offits extremes of variableipitclriii"arnetv eters-in. this;v case; maximum pitch" diameter" substantially. as ,indicated in. Figure 41:1 Adjuster ing. screw:A 8| may thereafter befresetnasrneeded to compensatef for 1l subsequent stretch' inuv -belt 81;? AnyY suitable-.means may: bel providedatorlocls the.y eccentric` mounting` block` z 92-insitsr aduste'd position such. asi forfrexample,v setf-.screwrl 92W 65' (Figures l and 3)* coaxiallyl with theeh'eadV stock center |2-. Pulley |09m`ay''beconstructed as a unit-with thef-aceplate-'BB or thetwoamay be secured together coaxially in anyfsuitable manner and as a unit' are rotatably supportedon a heavy studl shaft |0 2-`.whichis rigidly carried orfsupported within the head-'stock casinggand which projects throughtherightf end 'wall thereof-'andalso through:` thefaceplate 66, andin that end `it has a taperedfhole-'injwhich thee-tapered shank of vcenter |2'which-'needf net rotate; fits- As indicated` in Figure l; the inner^ends5of "the stud shaft |02 and thepulley-supporting: part Sil-92 are closely adjacent and; as; indicated-*in Figure 3,v` they are verygnearlyl coaxial;a-hbley extends axially through; thev stud shaftv 9|1 and also through themounting block 92,-; andfa :larger noie extends axially. throughfthe stud-^shafr=mii by removing the belt guardI cover (Figuresgl and 2),l a rod-v may :bef extended throughthj'ese holes to engagegthefin-ner en d of center-lrwlien it is necessary todislodge the same.

The described tra-in of vdrive,froniginotorshaft 18; to the face plate y|56` proyides au substantial speed reduction; sol thatthe Work-piecejW* (Fi'gfj urel)l may beerotatedL relativelyslowly"atfsub= stantially` const ant'-l speed, a" speed1 selectable-1 by the cone yor steppedjpulleys and-94andbelti according `to the diameter ofthe, work iWQto pro videan appropriate maximum surfacespeedtof presentation of the work-5to the grindingwheel; the pitch diameterof variablepulley-S-being the maximum'as showninFigureA; with" them'ovable motor 'H3l and,A itssuppcirirf-'Iinv normal'for `'at-"- rest full-line vposition Aas -shown VinV FigureV 3i At such maximum wor-ksurfaceespeed," grinding wheel 5 f'commences to grindthe rotating lworki piece- Wl and is fd-toward jthe axis ofitlief-latterat preferablyafsubstantialfrate, as-'by th'elfiyl draulic motorr 43(Figureso'andxfabovefde scribed, morder toeachi'eve high-ratey ofmaterial removalfrom the workTW, inseffectfaccompli'sh ing so-called rough grind-ing; whereuponf-'asffis later describ'edthe rate'of'feedof grindingwheel is lessened andfratefof drive -of@'theworki'W-"is reduced" inn correlations therewith so as to: remove less., and'less.. sto'ckffromffthe work.y and.A at diminishing surface speedsofffthelatter-tof-con' clude the grindingoperation with'nish grinde ing. According to myeinventiongl provide-means for reducingthel pitch: diameter ofi pulleyal-on motor shaft. "l 8 -to idiminish'l the-surface speed :of the work,y and lin -the v:preferred for-rn'l loflfmy" invention I employ -a hydraulicmotor; I Dlt-for "that purpose and coacting Withf-th'e-Thydraulicxmotor Y 7 constructed as shown-in Figure 4; it has a hub by which it may be keyed to motor shaft 18, as at |058, and externally it carries two disclike. sheave parts |06 and |01 providing juxtaposed inclined faces |08 and |09, respectively, with inclinations, substantially as shown, appropriate to the inclined side faces of a so-called V-belt but which is more usually of trapezoidal cross-section, substantially as shown in Figure 4. While iiexible, belt 81 made in known manner of rubber-bonded plies of fabric which extend transversely of its cross-section as shown in Figure 4, has substantial transverse rigidity and rides the pulley or sheave by engaging its inclined side faces respectively with the inclined faces |08, |09 of the sheave plates and at a' radius which is changeable according as the axial spacing between these inclined faces |08, |09 is changed. Suitable provision is made for changing this axial spacing; sheave disc |06 may be integrally formed with the hub |05 and at one end of the latter, while sheave disc |01 is slidably carried by the hub |05, being itself formed with a hub for that purpose and by which it is also splined to the hub |05, as at ||2, so it will rotate with its companion disc |06 even though it changes its axial position relative thereto. Provision is made to control the shift of sheave disc |01 axially and thus change the pitch diameter of pulley 86 to vary the rate of drive of vface plate 66 from that selected by means of the cone pulleys 90 and 94 and belt 95. Such means is under the control of the just-mentioned hydraulic motor |04 which functions, as above mentioned, in correlation with the hydraulic motor 43 that actuates the grinding Wheel feed. Hydraulic motor |04 comprises a cylinder H4 (Figures 3 and 6) suitably mounted and provided with a piston ||5 and piston rod ||6 which extends through a stuffing box |1 in cylinder head ||8 and which at its outer end has secured to it a bracket |20 which is pivotally connected by a pin |2| to a bracket extension at the rear (Figure 3) of the motor mounting plate 16 and at a point remote from the hinge pin 13 of the latter, and thus motor and its shaft 18 with pulley 86 may be displaced, about hinge pin 13 as an axis, throughout the range earlier above mentioned and thus change the distance between fshaft 9| (Figures 1 and 2) and its own shaft 18. Y Suitable provision is made to compensate for the arcuate path of movement of the connecting pin |2| as motor support swings about its pivoting axis, and this may comprise a U-shaped yoke |22 (Figure 3) secured to the rear wall of the head stock casing and between the arms of which cylinder I i4 is pivotally supported near its upper end by trunnions or pins |23, |24 (Figures 3 and 6) so that the hydraulic motor is self-adjusting to change in angularity of the motor support 15, as indicated in the full-line and broken-line positions shown in Figure 3. Bracket |20 conveniently serves to coact with the adjustable stop screw 8| which is preferably carried, as shown in Figures 3 and 4, by a bracket extension provided in the upper end of upper cylinder head H8 whereby they can more directly take up downward thrust (see Figure 6) caused by the piston ||5 and thus limit its downward stroke of movement according to the setting of screw 8|. Variablepitch sheave or pulley 86 (Figures 2 and 4) is made to change its pitch diameter according to the movement of piston ||5 of hydraulic motor |04 and thusvcorrespondingly to Vvchange thesurface speed of the driven Workpiece W. The left end of pulley hub |05 (Figure 4) carries a large diametered collar |26 keyed or splined, as at |21, and locked against axial movement by a setgscrew |28 and thus held in appropriatespacing from the slidable sheave disc |01. Collar |26 serves as an abutment or anchorage for one end of a spring |30, the other end of which abuts against sheave disc |01, yieldably forcing the latter to the left in Figure 4 away from collar |26 and toward the companion sheave disc |06.

Spring |30 may be of any suitable construction, illustratively it may be a spiral helix, so that as the spacing between collar |26 and disc |01 diminishes, the turns of the spring are accommodated one within another, thus to occupy a minimum of space when the spring is compressed to its maximum. Collar |26 and sheave disc |01 may be flanged toward each other and dimensioned so that the two may telescope as indicated in broken lines in Figure 4 when disc |01 reaches its extreme position to the right, a position in which the pitch diameter of the pulley IUE-|01 is smallest, and the belt 81 rides against the lower portions of the inclined faces IUS-|08, appropriately clearing the hub |05. Parts |26 and |01 are shaped to provide appropriate seats for the end turns of spring |30 which may be held therein in any suitable manner.

Spring |30 is relatively powerful and sufficiently so to maintain endless belt 81 taut, causing sheave plate |61 to move to the left in Figure 4 and the belt to ride at a larger radius should the belt be given any slack, as by decreasing the distance between motor shaft 18 and pulley 88 and, conversely, spring |30 yields and permits sheave plate I 01 to move to the right and belt El to ride at a lesser radius when the distance between motor shaft '58 and pullef,7 88 is increased; in the former case the speed of drive of pulley 83 is decreased, as is also the drive of the face plate |66 and the work W, and in the latter case the drive of these parts is increased. Abovedescribed hydraulic motor |04, by shifting motor 10 relative to the axis of pulley 88 determines the spacing between. motor shaft 16 and pulley 88 and the rate and direction'in which that distance is changed, correspondingly to determine the rate of drive of the workv Wfin correlation to the rate at which grinding wheel feed takes place. llustratively, for any selected ratio of drive by means of stepped pulleys S0 and S4, the speed of drive of the face plate may be diminished from a maximum value to onehalf corresponding, respectively, to maximum pitch diameter of the variable-pitch drive pulley 86 and minimum pitch diameter thereof; where round work is being ground of a diameter on the order of two or three inches, that for illustrative purposes may represent a change in speed or vdrive of the work W from about 60 R. P. M. to

30 R. P. M.

Referring now to Figure 6, hydraulic motors 43 and |04 are included in afiiuid pressure system which comprises a suitably driven pump |32 which draws liquid through pipe |33 from a reservoir |34 provided within the base I8 of the machine; its output is connected by pipe |35 to a control valve |316, pipe |35 also having a connection through pipe |31, and a suitable pressure relief valve |33 back to the reservoir |34, Valve |35, which may be of the piston type andprovided with pistons and p-orts substantially as indicated in Figure 6, has an outlet port connected byY pipe |40 and pipe |4| through cylinder paslever F65 (Figure l).

ksolenoid-actuated type, having an -enclosedsole.

lhydraulic motor |94 (Figures Gand -3') .-worlz W. The operator'nowmomentaril lever |55 "counter-clockwise in .Figure :6, .vmentarily closing switch -Hwto-energize relay sages m2 in .hydraulic .motor #aan .letterarie 'chamb'er |43 of motor. 43., andi'connectedbylle .hydraulic motor |54. Valve |36 has another -outlet connected .by pipe |=40,..pipe Ulf-.throttle valve |48, fand .pipe 453, throughvcylinder'passages |5|, .to the right-hand chamber. |52f'0f :hydraulic :motor 43 'and Aconnected by pipe |46, pipe |53,

throttle valve 45, and pipe |55 to `the/upper "chamber l|55 of hydraulic motor |04. Valvel |35 e: 'has another outlet connected aby pipe |51 f-toz dis- -Jcharge into theV reservoir'lS. Throttle valves |43 and |54 are unidirectionally shunted or,v by- --passed by ycheclr` valves |58 and |50, respectively, :by respective pipe connections as :indicated .in

Figure 6, the check valves permitting flow only in the respective directions of .the arrows as shown.

'Head stock driving motor i0 may bestarted and stopped by any suitable 'controLpreferably at the front of the machine, as 'by a pivotedrlever |51 (Figure l); lever` |`5| is shown also :inFigu-re 6, and through suitable relays 'anda-a mainimotor switch, diagrammatically Yindicatedfat |62,

-motor i may be connected or 'disconnected from;

the .power line 'm3-|64. Valve |35 ismanually lcontrollable in any suitable mannenvpreferably from the front of the-machine, Aas fbyfpivoted Valve |39 mayfbe of the noid |67 which when -de-energized permits `a spring |69 to shift and holdvalve. piston |39 rin an at-rest position shown 1in Figure fand-which when energized shifts and holds the valve-.pis-

ton to the left, compressing spring |59; leverlli.v

accordingly controls'the openingfand I:closing of .the circuit of solenoid '|61 which receives its energy from the power line IBL-|64.

An illustrative control circuit isshow-n yin'llligure 6 and comprises a normally vclosed switch n'I6-8 and a normally open -switchl-l, yeitlfierof Awhich vmay be momentarily operated .according as which one of two spring-opposed plu-ngers l|.||

andfll? is actuated yto the right by leverr|-66 which is pivoted at |13 to coact -Withthe plungers.

so that only one or the other is movedgto the vright according to the direction in'f which llever Hit is tilted, the plunger springs -|'|5,.|16 normally holding lever VIiifi in neutral onmideposition. v

With motor (Figure 1) driving grind-ing wheel l5 and the circuit of head-.stock motori!!! closed in response to actuation of--startand-stop lever |51 so as to drivethe work-holder oriarfbor i4 of the work-piece Wl thereon, grinding fwheel slide 28 is given a .position vwherein 'grinding vwheel i5 is just about ready toengagethe rotating Work W and is ready to be givenanninfeed movement; wheel slide 428.may bensorposivtioned 4by Yany suitable known means, illustratively by the aboveementionedhydraulic.rapid traverse mechanism, ,as in Fig-ure Y50i -SilVen-Patent No. 2,522,485, by which the feed screwfand Wheel slide of half-nutare bodily shiftedl'forvwardly and halted., whereupon -in-feedensues by` Yrotation of the feed screw. The piston .||5=tfof .in Vllowerniost position -as ydetermined -bytliegastop :screw 8|, fixing av spacing 'between .variablepitch pulley 33 and pulleyfil (Figures 2 and 3) that rcorresponds to maximum pitch Idiameter .int-pulleyeand Vhence maximum speed offdriveof-.the hifts :m0-

. through the valve toppipe |40 from .-whichgpipe :iM-suppliesliquidi-under pressure tothe left .|51 :in-1a circuit .froml-i-ne v|63,.conductor A83, V.solenoid .4 GLucOnd-uctor 84, switch I 82,. conduc- :torlv 1:85;v switch |08, and 'by conductor l -1-8 `tol-inc Ev|-'|4, 'therebyishiftinglthe valve piston to the left Whereit. is held until-solenoidy |61 is ,deenergiced :Relay |11 hasan auxiliary switch-I 8E whichis noid -lthus remains energized until. lever. |'6`6 Yis tiltedffafterconclusion. of the grinding opera- 20- -itionl (Figure `6) to momentarily. open switch |00.

tion fiabouttofbe described, in clockwise L.directhi-1s de-.ener'gizing relay |11 -irestore ...its Aswitches |82 and :|85 to open position.

-With valvefpistonl |39 .held in .its .left-hand, positionftherdischarge. of pump |332 lis--..con.necte.d

chamber |43 of grinding wheelffeed .hydraulic `jrnotorf' 43,-andpipe |44supplies :it rto .lowenc'hamber -145 of the..speedchange .control .hydraulic V.n'iotor- |04; piston-46 v'of .the=.former rmovesto the .rightl in: Figure 6, and piston l .I5 ofthe V.latten-commences -to move upwardly. .Grind-ing commences, Ithe-,grinding wheel .beingsteadily 'iedtoward `the-axis .of the rotating. work W.,..the movi-ng .pister-146 'rotating the eed:.screw ..33 y-fin `i-n-feed f direction by Y the mechanism abovede scri-bed. in connection with Figure. .5.;at theirst `"grinding contact of grinding wheel with the work `W, the..latter is rotating at vrnaxirnurri-.:-ipee .i,.giet'- .fing the.-tworkra high-.surface speed commensurate with Vniaximinn#ratei of material removal `appro- ;-priate to thevcutting ,characteristics-of the :grinding .wheel fand .to the. :composition ofthe workpiece As grinding .and wheel inefeedcon- -.-tinue, rate .of drive-of the work W. decreases, Isomewhat -commensurately decreasing .rate fof 1lustrative,embodiment, are controllable by means l-of. tlirott1e#valves.-Maand |54 @Figure =6) 'which -kcontrol"thenespective rates atwhich vliquidfis :permittedto-iescape..from the othersides-:iof the material removal,` .and the decrease I. in...s,urace f-speed 1continues,..vuntil-t'he Work- W..is yjust tabout brought fdown .to Vsize by .which .time surface speed, with the Yillustrative rigures earlier .above fgivemfmay bereduced to half 4of-fits startingisurface speed.

The respective rates fof. .grinding .wheel vin-feed and :of change iny worksurfacerspeed, .in thailfclfargefromfchamber |52 fof motori-43 isl byciwa'y of cylinder channelsfflilfpipe |50,throttle.ivalve lT48, 1p1-pe l-dflgpipe 'f 14B which' Astands connected,

:6.5fwicanftherpistonwaive 1am@ discharge-ipipe'm leading-back' rito Lreservoir' |34 throttle valve '|48 yisadjustableorcontrollarne infanysuitabie manlner, 4fi1lustra'tive'ly manually, itbeing notelf'that |48. The'otheVc'harnber |56 vof speed-'control passingl dffthrottle `'valve |54, whichisalso valdjustable or controllable in any suitable manner, preferably manually.

For example, throttle valves |48 and |54 may be set or controlled so that the two hydraulic motors 43 and |64 conclude their respective strokes at just the same time whereupon the operator may thus permit the grinding wheel to be held in a nxed position to spark out and conclude the finish grinding at the lowest work surface speed, the operator himself controlling the period of such a dwell. Or these throttle valves may be set so that piston 46 of feed motor 43 comes to rest at the end of its stroke in suitable time before piston comes to the end of its upward stroke, and in such case there results ar dwell or halting in the in-feed of the grinding wheel to conclude nish grinding and sparking out at continued diminishing work surface speed. Or throttle valves |48 and |54 may be set or controlled so that the speed-change motor piston l5 reaches the end of its stroke at 'any suitable time just prior to the conclusion of the in-feed stroke of feed-motor piston 46, in which case nnish grinding at constant low surface speed of the work W at controlled wheel infeed may be had, followed by sparking out during a suitable dwell after the feed-motor piston 46 comes to a halt.

, The stage of iinish grinding and sparking out having been concluded, the operator actuates lever |66 clockwise in Figure 6 to momentarily open stop switch |58, thus de-energizing solenoid |61, whereupon valve piston |39 assumes the atrest position shown in Figure 6. As a result the pipe connections to the two hydraulic motors are changed and both are actuated in reverse direction at maximum speed, unaffected by the throttle valves |43 or |54. The output of pump |32 now stands connected to pipe |46 so that 'liquid under pressure flows to chamber |52 of feed-motor cylinder 44 through pipe |41, check valve |58 (by-passing valve |48), and pipe |56, rapidly moving piston 46 to the left and rapidly rotating feed screw 33 to retract the grinding wheel, and that liquid under pressure flows through pipe |53, check valve |60 (by-passing throttle valve |54), and pipe |55 to the upper chamber |56 of the speed-change motor, rapidly lessening the distance between motor shaft 18 and pulley7 S8 and causing the spring |30 (Figure 4) to increase the pitch diameter of pulley y86 and restore the initial high-speed ratio of drive of the head stock face plate 66. As piston 46 of motor 43 moves to the left, liquid is discharged from its left-hand chamber by way of passage |42, pipe |4|, pipe |46 which, through the valve |36, is connected to the discharge pipe |51 that leads to reservoir |34; the downward movement of piston H'of motor |04 causes discharge of liquid from chamber |45 through pipe |44 and pipe |46 which, through valve |36, is connected to the reservoir return pipe |51.

The quick return of the parts to starting position permits the operator to start removing the arbor I4 from the machine and replace it with witvli many thoroughly practical advantages are successfully achieved.

It will be seen that the apparatus is of compact, rugged, and easily controllable construction and arrangement and is well adapted to meet the varying conditions of hard practical use. The apparatus is well adapted to achieve high efficiency of grinding action, being capable of high cutting rate as in initial or rough grinding stages of a grinding operation, and yet in the same grinding operation good precision and effective finish grinding are achievable.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawing, is to be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. In a grinding machine, in conioination, a grinding wheel, means for rotatively supporting va work-piece to be ground and driving means therefor comprising motive means having a driving connection with said rotatable work-supporting'means that includes two pulleys and a connecting drive belt, one of said pulleys having spring-biased coacting belt engaging members which are relatively movable in axial direction for changing the effective pitch diameter thereof whereby to change the ratio of drive between said two pulleys and thereby change the speed of drive of said'work-supporting means, means movably mounting one of said pulleys for 'movement in a direction to change the distance between it and the other of said two pulleys and thereby effect change in the ratio of drive therebetween, means for effecting relative feeding movement between said grinding wheel and rotatable work-supporting means during 'grinding action of the grinding wheel on the rotating work-piece and for eiecting relative retracting movement between said grinding wheel and the work-supporting means, and reversible motor means operating at relatively low speed in one direction of drive and operating at relatively high speed in opposite direction of drive and having operating connections with said pulley mounting means to move it to change the aforesaid ratio of drive, with means for controlling the direction of drive of said motor means to effect lowspeed movement of said pulley mounting means during relative feeding movement between said grinding wheel and said work-supporting means to move said pulley mounting means and thereby change the speed of drive of said work-supporting means and to eiect high-speed .movement thereof for resetting the machine for the next cut by the grinding wheel.

2. In a grinding machine, in combination, a grinding wheel, means for rotatively supporting a work-piece to be ground and driving means therefor comprising motive means having a driving connection with said rotatable work-supporting means that includes two pulleys and a connecting drive belt, one of said pulleys having springbiased coactingr belt engaging members which lare, relatively movable in axial direction for changing the eifective pitch diameter thereof whereby to change the ratio of drive between said two pulleys and thereby change the speed of drive of said work-supporting means, means comprising a reversible piston-and-cylinder fluid motor for eifecting relative feeding movement -between said grinding wheel and said rotatable work-'supporting means during grinding action for eiecting separating movement therebetween,

' elements.

'fcylinderi-uid'vmotor*fori-controllingfsaid'rblten- Vgaging members' of saidonepulleyaisourcefof fluid under pressure,fand IVvalv'efnieans for -eontrolling-'the eiective fluid/'flowto v*saldi-two motors motor at relatively lowspeed lfor eie'cting relative axial movement -of said belt-en'gag'inglmem- -bers of said-one plleyin a directionltoldiminish the ASpeed 0f driveof -sa'dA VWoi-k-'suppoiftingmeans Lifo TWorkesupporting meansgandf means :operabi'eifin to drive both Ymotors in reverse directionnel/elatively high'speed fon-respectively; relatively rapid movement of `separation ybetween*thegrinding :wheel and the work-supporting means and f rela- 'ing moti-veimeansfvnavingaa driving feonneton 'with-said woi'ksupportin-g means lthat'inchides ftWof-pulleysfand fa-*conneeting f'di'five zbeliaffoneof said ,pulleys having coacting :relatively f-'mov'able vtodrivesaidflrstfinotor'atla relatively tlowfspeed ,f5 parts .'ffor hangin'gv'fthe effective'pitch-diameter "for feeding lmovement and '-to ldrive*said l:second thereof and `for -'thereby changing'theratio fof drivebetween 'said'f two pulleys, Irnea'ns i or i effecting a f controllable ramount of 'relative' fe'edin'g Vmovementl'betweenfsaid lgrindingiwheel and: vvsaid timed relation tof'said 'relative ffee'ding movement, 'said-llastmentioned imeans 'comprising la :pistone and-cylinder :fluidffmotorhaving connectionsfefyfective during fa-'str'eke offsaidm'otor lfor operattively7 rapid axial movement between sa-idl'belt- `I`i5 ing-u-p'onsaid relatively movable members dffs'aii Lengaging -members in la direction --to increase v-the 'speed of v`drive of said -Workesuppor'ting means.

v-3.n v'a'lgrinding machine, in combination-'a r'grinding fwheel, 4means 'for -rota'tab'ly supporting piilleyfand5 upon. `saidlbe'lt to 'change 'the effective' pitch diameter oflthefforme'rfandfto gm'aintain ldrivingftension 'of theb'elt-with change inf-pitch "diameterandcontrol-meansfor timing '.th'e f'ic'ona Work-piece rto 'be ygrotnd-"and :driving-means *'20 clusion of 'the s'troke'of Lsaid piston-.and-cylinder v"therefor comprising Va diven'pu'lley andamotor having a-'drive pulley oonnectedloyla driving be'lt with -said driven pulley, Aonefof-said 'fpulleys'nav- "ingA fcoactingbelt 'engaging members which are relatively movable in axial fdireotion'for -Shang- Ving theeifective pitch diameter-thereof whereby thev ratio fofr drive between ysaid v"two Lpulleys-iis fchangeablefmeans forsupporting said motor'an'd its: drive pulleyf for -movement v`toward andlaway change 'its eiiec'tive pitch diameter, means lfor `effecting relative feeding movement vbetween'saifzl f grinding wheelv and said work-supporting -ineans duringgrindingfaction, va fluid motorlliaving Ya lcylinder* element 'Y and a coacting piston Ielement `and having* operating connections with said motor supporting meansan'd operable-during'said vrelative feeding movement `to elect `movement of said 'motor-supporting meansand fth'erebyf'control the-spacing and the ratio off drive l'between said vtwo pulleys, and means operating -to-con'trol the action -o'f said fluid motor-comprising valvefizf) lmsi-mentifm@@meansComprisingmeans means for the 'motor-operating 'uid 'and means for selecting `the range 'of movementof saidfmoter-supporting means toward anda'vvay frornfsaid other pulley.

v'motor 'inf relation "toas'aid fcoritrllable amount "f relative feeding movement.

-6.' In fa grinding-machine, in combination, a grinding wheel, meansffor supporting 1aw`ork 2T piece 'tofbe ground, power-drivenrmeans"driving said -work-supportingl means yto traverse "-tlie surface of a ysupported fworkep'iece relative cto said grinding Ywheel, said power-driven frneans inoliiding motive -means 1having a driving fconnne'ction two pulleys and aVJ connecting d'rivebe'lt, lone f said pulleys comprising two'members-having 'aid- :jacent fru'sto''conical faces forengagng/Ttherbel-t -with spring means y'a-Xially, biasing one tf'Sald members totvardthefotherto increase the i'e'iective 'pitch diameterfthereofpreversible 'fluid motor means `operating Ein reversible strokes for 'iecting relative feeding movement foetvveen lsaid grinding wheel and -said lworkesupporting -means 40 and yforleifecting separating movement 'therebetween, yand means voperable during :said :relative movementand '-'afiecting `'the pitch 'lfdi'amete'r of 'said one piille'y `Aand `Iaffecting said "belt to change the =ratio-cf -drive'b'etween said =twov piil1eys, isaid mount- Aing oneof said pulleys iforlmovement in :irenvtion Ltoward andfa'way 'fr'orn' 'the other andreversb -ble fluid #motor means 'operating iin l`re've'r'sible strokes for :operating- :uponfssaid ipulley Lmo'unti'ng 4. A Agrinding machine as claimed fin' claim-?, t() means to Change-heiistame zbefweensaifibw'o in Whichsaid motor supporting-means comprises a pivoted support for the motor-withthe laxis of pivoting parallel to and folset'vfrom :the-axis of said drive pulley whereby shifting of the 'sup- .port about -its axis shifts the motorland said drive pulley toward or away 'from 'the other pvilley and said range-selecting 'means oomprisingaw 'instable -stop means enacting with said :motornsupporting means vand iny which said yoperating 1pulleys, ^a source-of' pressure fiu'id for' saidftwo iluid-motor'mean's, main icontrol valve Lmeans, Which-infone'position connects said source` tolbo't'h of said fluid motor means to actuate eaoh-iinione "5 v"strokearilein' another-positioniconnects them to connections between said fluid -lm'otor fand said 560 .grinding 'WheeL-lmeansfffor supporting@J worm pivoted motor-support comprise anarticlat'ed connection between the Y'latterffafta point space-:l from its pivotingaxislanzllone of said fiuidfmotor elements and means pivotal-ly 'supporting the other o'f saidrnotor elements forfself-'a'ccomable-'speedfdrivingconne ,tionfwithfisaid fyi/gorie modation'o'f the duid motortotheswing-o'f'said I motor support as it pivots in VVresponse tto relative movement between the'pistomand-cylinder 5. In a grinding wheel, meansfor xsupporting a Wo`rk 1 pieceto b'efground, l power-driven 'means'dilving saidvvork-supportingme'ans to; traverse fthesurface lof a supported workf-piecejr'elative-"td-said grinding wheel, said poW'e'r-driven-'me'ansinoltidgrinding machine, in combination,k ao

76 andi-said work-suppe ting meanspmeanstmii-eontrolling the relative positions of said relatively shiftable members of said pulley and for controlling the relation of said belt to said two members and to the other pulley to change the effetcive pitch diameter of the pulley and to maintain driving tension of the belt with change in pitch diameter, means to actuate said controlling means in a direction to decrease the rate of drive of said work-supporting means and thereby decrease the surface speed of the work-piece as the grinding action of said grinding wheel thereon progresses, and controllable means for setting the relation between the time period of operation of said actuating means and the time period of the means for effecting said controllable amount of relative feed movement between the grinding wheel and the work-supporting means.

8. In a grinding machine, in combination, a grinding wheel, means for supporting a workpiece to be ground, power-driven means driving said work-supporting means to present the surface of a supported work-piece to said grinding wheel, said power-driven means having a variable-speed driving connetcion Iwith said worksupporting means for changing the surface speed of the work-piece, said driving connection including two pulleys and a driving belt, one of said pulleys having coacting relatively shiftable beltengaging parts which change the effective pitch diameter of the pulley according to the position of one of said parts relative to the other, means for eifecting relative feeding movement between said grinding wheel and said work-supporting means and thereby control depth of cut of the grinding wheel on the work-piece and for effecting relative separating movement therebetween, means for controlling the relative position of said shiftable members of said pulley and for controlling the relation of said belt to said two members and to the other pulley to change the effective pitch diameter of the pulley and to maintain driving tension of the belt with change in pitch diameter, and means operating in timed relation to said feeding movement to actuate said controlling means at a relatively slow rate in a direction to decrease the rate of drive of said work-supporting means and thereby decrease the surface speed of the work-piece during grinding and operable during relative separating movement between said grinding wheel and said work- -supporting means to actuate said controlling means at a relatively high rate in a direction to ,increase the rate of drive of said work-supportf piece to be ground, power-driven means `driving said work-supporting means to present the surface of a supported work-piece to said grinding wheel, said power-driven means having a variable-speed driving connection with said worksupporting means for changing the surface speed of the work-piece, said driving connection including two pulleys and a driving belt, one of said pulleys having coacting relatively shiftable beltengaging parts which change the effective pitch diameter of the pulley according to the position of one of said parts relative to the other, means for effecting relative feeding movement between said grinding wheel and said work-supporting means and thereby control depth of cut of the grinding wheel on the work-piece and'for effecting' relative. separating movement therebetween, means comprising a reversible motor for controlling the relative position of said relatively shiftable members of said pulley and for controlling the relation of said belt to said two members and to the other pulley to change the eective pitch diameter of the pulley and to maintain driving tension of the belt with change in pitch diameter, and means operable during said relative feeding movement to actuate said motor at relatively low speed in a direction to decrease the rate of drive of said work-supporting means and thereby decrease the surface speed of the workpiece during grinding and operable during said relative separating movement to actuate said motor at relatively high speed in a direction to increase the rate of drive of said work-supporting means.

10. In a grinding machine, in combination, a grinding wheel, means for supporting a workpiece to be ground, power-driven means driving said work-supporting means to present the surface of a supported work-piece to said grinding wheel, said power-driven means having a, variable-speed driving connection with said worksupporting means for changing the surface speed of the work-piece, said driving connection including two pulleys and a driving belt, one of said pulleys having coacting relatively shiftable beltengaging parts which change the effective pitch diameter of the pulley according to the position of one of said parts relative to the other, means for effecting relative feeding movement between saidgrinding wheel and said work-supporting means and thereby control depth of cut of the grinding wheel on the work-piece and for effecting relative separating movement therebetween, means comprising a reversible motor for controlling the relative shift between said shiftable members of said pulley and for controlling the relation of said belt to said two members and to the other pulley to change the effective pitch diameter of the pulley and to maintain driving tension of the belt with change in pitch diameter, a source of fluid under pressure for actuating said motor, and means operable during said feeding movement to supply said motor at a low rate with uid from said source for actuating it in a direction to decrease the rate of drive of said work-supporting means and thereby decrease the surface speed of the work during grinding and operable during said relative separating movement to supply said motor with fluid at a relative high rate to drive the motor in reverse direction.

11. In a grinding machine, in combination, a grinding wheel, means for supporting a workpiece to be ground, power-driven meansdriving said work-supporting means to present the surface of a supported work-piece to said grinding wheel, said power-driven means having a variable-speed driving connection with said worksupporting means for changing the surface speed of the work-piece, said driving connection including two pulleys and a driving belt, one of said pulleys having coacting relatively shiftable beltengaging parts which change the effective pitch diameter of the pulley according to the position l of one of said parts relative to the other, reversible motive means operable in one direction to eifect relative feeding movement between said grinding wheel and said work-supporting means and operable in reverse direction to effect relative separating movement therebetween, means including a reversible motor for controlling the relative shift between said relatively shiftable members of said pulley and Vfor controlling the relation of said belt to said two members and to the other pulley to change the effective pitch diameter of the pulley and to maintain driving tension of the belt with change in pitch diameter, said reversible motor operating at a low rate in the direction to decrease the rate of drive of said work-supporting means and operating at a high rate in the direction to increase the rate of drive of said work-supporting means, and interdependent controls for said reversible motive means and said reversible motor for substantially synchronizing the low-speed drive in direction of said reversible motor with said first-mentioned direction of drive of said reversible motive means and the relatively high-speed drive of said reversible motor with the drive in reverse direction of said reversible motive means.

12. A grinding machine having a longitudinally extending table and a transverse slide supporting a grinding wheel, said table having thereon means for rotatably supporting and driving ra work-piece for action thereon by said grinding wheel, said means comprising a head-stock unit having a driving motor and drivingr connections that include a drive pulley driven by said motor and a driven pulley and a connecting belt therebetween, said drive pulley comprising two coaxial relatively shiftable belt-engaging parts with spring means coacting therewith to bias one toward the other to increase the effective pitch diameter thereof, means mounting said drive pulley for movement in a direction to increase the distance between it and said driven pulley and thereby cause the belt to oppose said spring means and lessen the pitch diameter thereof,

thereby decreasing the rate of drive of said driven pulley, means operating upon said wheel slide to eiect feeding movement of the grinding wheel toward a work-piece supported in said worksupporting and rotating means and to determine the depth of cut of the grinding wheel on the work-piece, and means for diminishing the rate of cutting action of the grinding wheel on the work-piece comprising means operable during the feeding movement of the grinding wheel slide to move said driving pulley mounting means in a direction to increase the distance between said two pulleys and thereby diminish the rate of drive of the work-piece.

13. A grinding machine as claimed in claim l2 in which there are provided stop means coacting with said pulley mounting means to limit the range of movement thereof and the range of change of speed of drive of the work-piece.

14. A grinding machine as claimed in claim 12 in which said means for mounting said drive pulley for movement in the opposite direction comprises said motor and a movable carrier therefor associated with said head-stock unit, said drive pulley being carried by the motor shaft and said means for moving said pulley mounting means operating upon said carrier.

15. A grinding machine as claimed in claim 14 in which said carrier is movably associated with said head-stock unit by a pivotal connection therebetween the axis of which is parallel to and displaced from the axis of said driving pulley.

16. A grinding machine having a longitudinally extending table and a transverse slide supporting a grinding wheel, said table having thereon means for rotatably supporting and driving a work-piece for action thereon by said grinding wheel, said means comprising a head-stock unit having a driving motor and driving connections i8 that include a drive pulley driven by said motor and a driven pulley and a connecting belt therebetween, said drive pulley comprising two coaxial relatively shiftable belt-engaging parts with spring means coacting therewith to bias one toward the other to increase the effective pitch diameter thereof, means movably supporting said motor from said head-stock unit for reversible movement in directions to increase and decrease the distance between said two pulleys whereby, upon increase in said distance, said belt opposes said spring means and the pitch diameter of said drive pulley is decreased and, upon decrease in said distance, said spring means is effective to increase the pitch diameter of said drive pulley, means operating upon said wheel slide to feed the grinding wheel toward said work-supporting and rotating means to determine the depth of cut and operable to retract the wheel slide and grinding wheel, and means for diminishing the rate of cutting action of the grinding wheel comprising means operable at a relatively low rate and during feeding movement of the grinding wheel slide to slowly shift said motor in a direction to increase the distance between said two pulleys and thereby relatively slowly diminish the surface speed of the work.

17. A grinding machine having a longitudinally extending table and a transverse slide supporting a grinding wheel, said table having thereon means for rotatably supporting and driving a work-piece for action thereon by said grinding wheel, said means comprising a head-stock unit having a driving motor and driving connections that include a drive pulley driven by said motor and a driven pulley and a connecting belt therebetween, said drive pulley comprising two coaxial relatively shiftable belt-engaging parts with spring means coacting therewith to bias one toward the other to increase the effective pitch diameter thereof, means movably supporting said motor from said head-stock unit for reversible movement in directions to increase and decrease the distance between said two pulleys whereby, upon increase in said distance, said belt opposes said spring means and the pitch diameter of said drive pulley is decreased and, upon decrease in said distance, said spring means is effective to increase the pitch diameter of said drive pulley, means operating upon said wheel slide to feed the grinding wheel toward said work-supporting and rotating means to determine the depth of cut and operable to retract the wheel slide and grinding wheel, and means operable during feeding movement of said grinding wheel slide for relatively slowly shifting said motor in a direction to increase said distance between said pulleys to relatively slowly diminish the surface speed of the work and operable at a relatively high rate of speed to shift said motor in opposite direction during retracting movement of said wheel slide to restore the rate of drive to its initial relatively high value.

OIVA E. HILL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,162,832 Walker Dec. 7, 1915 2,103,464 Judelshon Dec. 28, 1937 2,272,048 Haas Feb. 3, 1942 2,394,209 Scuse Feb. 5, 1946 2,559,531 Belden July 3, 1951 

